21201221121021 has 12 divisors (see below), whose sum is σ = 30624732486972. Its totient is φ = 14133802910976.

The previous prime is 21201221121013. The next prime is 21201221121037. The reversal of 21201221121021 is 12012112210212.

21201221121021 is a `hidden beast` number, since 21 + 201 + 2 + 211 + 210 + 21 = 666.

It can be written as a sum of positive squares in 2 ways, for example, as 830567936025 + 20370653184996 = 911355^2 + 4513386^2 .

It is not a de Polignac number, because 21201221121021 - 2³ = 21201221121013 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21201221120985 and 21201221121003.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21201221121061) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 28318546 + ... + 29057571.

It is an arithmetic number, because the mean of its divisors is an integer number (2552061040581).

Almost surely, 2^{21201221121021} is an apocalyptic number.

It is an amenable number.

21201221121021 is a deficient number, since it is larger than the sum of its proper divisors (9423511365951).

21201221121021 is a wasteful number, since it uses less digits than its factorization.

21201221121021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 57417180 (or 57417177 counting only the distinct ones).

The product of its (nonzero) digits is 64, while the sum is 18.

Adding to 21201221121021 its reverse (12012112210212), we get a palindrome (33213333331233).

The spelling of 21201221121021 in words is "twenty-one trillion, two hundred one billion, two hundred twenty-one million, one hundred twenty-one thousand, twenty-one".